As an example of plasma processing, there is etching processing. Etching processing is performed by placing a substrate to be etched on a platen arranged in a processing chamber, supplying an etching gas into the processing chamber and generating plasma therefrom, and applying a bias potential to the platen.
By the way, the substrate to be etched includes a substrate having no resist film formed on the upper surface of a peripheral portion thereof, and in such a case, the portion where no resist film is formed of the upper surface of the peripheral portion of the substrate is etched. Accordingly, conventionally, as a device capable of preventing such a disadvantage, there is a jig for plasma etching 100 as shown in FIGS. 8 and 9, for example (see the Japanese Unexamined Patent Application Publication No. 2007-150036).
As shown in FIGS. 8 and 9, the jig for plasma etching 100 is made of a ring-shaped member and is formed to have an inner diameter larger than the outer diameter of a substrate K, and has a containing portion 101 within the ring of which the substrate K is contained, a contact portion 102 which is formed inside the containing portion 101 and is capable of being brought into contact with the upper surface of a peripheral edge portion of the substrate K, and an extending portion 103 which is formed to extend inward from the contact portion 102 and is provided at a position higher than the upper surface of the substrate K at a distance therefrom.
According to this jig for plasma etching 100, when the substrate K is etched, the jig 100 is arranged so that the contact portion 102 is brought into contact with the upper surface of the peripheral edge portion of the substrate K, thereby covering the upper surface of a peripheral portion of the substrate K with the extending portion 103 and the contact portion 102. Therefore, on the upper surface of the peripheral portion of the substrate K, ion incidence caused by a bias potential applied to a platen 105 is prevented and etching is therefore prevented.
However, when this jig for plasma etching 100 is arranged on the upper surface of the substrate K, it is hard to apply a bias potential uniformly in the vicinity of the portion covered by the extending portion 103 of the upper surface of the peripheral portion of the substrate K and therefore ions are not incident vertically on the substrate K and are apt to be incident obliquely thereon. Therefore, there is caused a problem that, as shown in FIG. 12, a side wall of a hole H or trench H which is formed by the etching is not perpendicular to the substrate K, for example, is inclined at a inclination angle α or β, and it is therefore not possible to obtain a highly accurate etching shape. It is noted that, in FIG. 12, a side wall when being inclined is indicated by the solid line and a side wall when being vertical is indicated by the two-dot chain line. Further, the reference M indicates a mask.
Therefore, it is necessary to arrange the jig for plasma etching 100 with high accuracy so that it is co-axial with the platen 105 and the substrate K. That is, as shown in FIGS. 8 to 11, in a case where, even if only a low accurate etching shape is obtained between the peripheral edge of the substrate K and a portion inward by a certain dimension d from the peripheral edge of the substrate K, a highly accurate etching shape is required in a region R (region of φD) located on the inner side of the portion inward by the certain dimension d, when the accuracy of arranging the jig 100 is low, the region R can overlap with a region S which is in the vicinity of the portion covered by the jig 100 (extending portion 103) and within which a highly accurate etching shape cannot be obtained, and it is therefore possible that only a low accurate etching shape is obtained also in the region R. Therefore, the jig 100 must be arranged with high accuracy so that it is co-axial with the platen 105 and the substrate K. It is noted that FIGS. 8 and 9 show a case where the accuracy of arranging the jig for plasma etching 100 is high and FIGS. 10 and 11 show a case where the accuracy of arranging the jig for plasma etching 100 is low.
Accordingly, the inventors have suggested a device as shown in FIGS. 13 and 14 as an etching device capable of improving accuracy of positioning a member for covering the upper surface of a peripheral portion of a substrate K. As shown in FIGS. 13 and 14, an etching device 100 is configured with a processing chamber 11 having a closed space, a substrate holding device 80 holding a silicon substrate K to be etched, a lifting cylinder 85 lifting up and down a platen 81 of the substrate holding device 80, a protective member 90 for covering the upper surface of a peripheral portion of the silicon substrate K held by the substrate holding device 80, a support body 91 supporting the protective member 90, an exhaust device 40 reducing the pressure within the processing chamber 11, a gas supply device 45 supplying a processing gas into the processing chamber 11, a plasma generating device 50 generating plasma from the processing gas supplied into the processing chamber 11, an RF power supply unit 55 supplying RF power to an electrode 82 of the substrate holding device 80, and other components.
The processing chamber 11 comprises a cylindrical lower container 12 and a cylindrical upper container 13 which each have an inner space communicating with that of the other, and the upper container 13 is formed to be smaller than the lower container 12 and is disposed on a central portion of the upper surface of the lower container 12. Further, two positioning pins 19 are vertically arranged on the bottom of the lower container 12.
The substrate holding device 80 has the platen 81 comprising the electrode 82 which has a disk shape, an insulator 83 which is formed on the electrode 82 and on which the silicon substrate K is placed, and a DC power supply unit 84 applying direct voltage to the electrode 82. The substrate holding device 80 generates a chucking force between the silicon substrate K and the insulator 83 by causing the DC power supply unit 84 to apply direct voltage to the electrode 82, thereby chucking and holding the silicon substrate K. The electrode 82 and the insulator 83 are formed to have an outer diameter larger than the outer diameter of the silicon substrate K so that their respective peripheral portions extend outward beyond the silicon substrate K placed on the insulator 83. It is noted that the platen 81 is arranged in the lower container 12.
The lifting cylinder 85 is connected to the lower surface of the electrode 82, and lifts up and down the platen 81 between a lifting-up end position and a lifting-down end position (waiting position).
The protective member 90 is formed in an annular and plate-like shape and is configured to be capable of being placed on a peripheral portion of the platen 81 (insulator 83). Further, the protective member 90 is configured to cover the upper surface of the peripheral portion of the silicon substrate K on the platen 81 with an inner peripheral edge portion thereof when being placed on the peripheral portion of the platen 81.
The support body 91 comprises an annular and plate-shaped lower member 92 which is arranged below the protective member 90 and is placed on the bottom of the lower container 12, and stick-shaped connecting members 94 connecting the upper surface of the lower member 92 and the lower surface of the protective member 90, and supports the protective member 90 between the lifting-up end position and the lifting-down end position. Further, the lower member 92 has two through holes 93 which are formed at positions spaced 180° from each other around the center of the lower member 92, the through holes 93 vertically passing through the lower member 92 and being engaged with the positioning pins 19.
The exhaust device 40 comprises an exhaust pump 41 and an exhaust pipe 42 connecting the exhaust pump 41 and a side wall of the lower container 12, and exhausts the gas within the lower container 12 through the exhaust pipe 42 to thereby reduce the pressure inside the processing chamber 11 to a predetermined pressure. The gas supply device 45 comprises a gas supply section 46 supplying a gas including an etching gas as the processing gas, and a supply pipe 47 connecting the gas supply section 46 and the upper surface of the upper container 13, and supplies the processing gas into the upper container 13 from the gas supply section 46 through the supply pipe 47.
The plasma generating device 50 comprises a plurality of annular coils 51 aligned vertically on the outer periphery of the upper container 13, and an RF power supply unit 52 supplying RF power to the coils 51, and generates plasma from the processing gas supplied into the upper container 13 by causing the RF power supply unit 52 to supply RF power to the coils 51. The RF power supply unit 55 produces a potential difference (bias potential) between the electrode 82 and the plasma within the processing chamber 11 by supplying RF power to the electrode 82.
According to the etching device 100 thus configured, the pressure inside the processing chamber 11 is reduced by the exhaust device 40 and a silicon substrate K is placed on the platen 81 which is at the lifting-down end position, and then direct voltage is applied to the electrode 82 by the DC power supply unit 84 and thereby the silicon substrate K is chucked and held. Thereafter, the platen 81 is lifted up from the lifting-down end position toward the lifting-up end position by the lifting cylinder 85. While the platen 81 is lifted up, the protective member 90 is placed onto the platen 81 and the upper surface of the peripheral portion of the silicon substrate K is covered by the inner peripheral edge portion of the protective member 90 and a structure comprising the protective member 90 and the support body 91 is lifted up together with the platen 81 (see FIG. 15).
Once the platen 81 is lifted up to the lifting-up end position, a processing gas is supplied into the processing chamber 11 by the gas supply device 45 and RF power is supplied to the coils 51 and to the electrode 82 by the RF power supply units 52 and 55, respectively. Plasma is generated from the supplied processing gas, and the silicon substrate K reacts with radicals generated by the generation of the plasma and ions generated by the generation of the plasma are made incident on the silicon substrate K by the bias potential, thereby etching the silicon substrate K. It is noted that, since the ion incidence is prevented by the protective member 90 on the upper surface of the peripheral portion of the silicon substrate K, the silicon substrate K are etched except the upper surface of the peripheral edge portion thereof.
Thereafter, once the etching is completed, the platen 81 is lifted down from the lifting-up end position toward the lifting-down end position by the lifting cylinder 85. While the platen 81 is lifted down, the lower member 92 is placed onto the bottom of the lower container 12 and the protective member 90 is separated from the platen 81 (see FIG. 13).
Thus, in this etching device 100, the engagement relationship between the through holes 93 of the lower member 92 and the positioning pins 19 on the bottom of the lower container 12 improves the accuracy of positioning the protective member 90 (structure comprising the protective member 90 and the support body 91). Thereby, deterioration of etching shape is prevented in a region located on the inner side of a portion inward by a certain dimension from the peripheral edge of the silicon substrate K.